Rotating disc electrode study of the electropolishing mechanism of NiTi in methanolic sulfuric acid

The mechanism during electropolishing of NiTi in methanolic 3 M sulfuric acid is elucidated based on the investigations carried out using a rotating disc electrode (RDE). The influence of the rotation rate, temperature and the addition of Ni and Ti ions in solution on the dissolution kinetics are investigated and analysed. The dissolution of NiTi during electropolishing exhibits Levich behaviour confirming mass transport as the rate-limiting step. The temperature dependence shows a typical Arrhenius behaviour and the activation energy for dissolution is Ea = 19.2 (±1.33) kJ mol−1. The addition of metal ions to the electropolishing solution results in a lower limiting current density for both, Ni2+ and Ti4+ addition. This confirms the mass transport of dissolved species from the anode surface to the bulk of the solution as the rate-determining step.